Tracking and erosion of HTV silicone rubber and suppression mechanism of ATH

Tracking and erosion of high temperature vulcanizing (HTV)-silicone rubber (SIR) and the suppression mechanism of alumina trihydrate (ATH) filler were investigated in the present study. The tracking and erosion resistance of HTV-SIR filled with 0 to 60%wt ATH was evaluated by employing an IEC 587 in clined plane (IP) tracking and erosion test, during which leakage current p ulses on HTV-SIR were counted. Surface temperature distributions and the oc currences of thermal spots >400 degreesC also were observed by means of an infrared thermovision study. We employed thermogravimetry (TG)-differential thermal analysis (DTA)-mass spectrometer (MS) to observe the thermal degra dation of unfilled and filled HTV-SIR in both air and argon. The test resul ts indicate that 40%wt is a critical ATH level and whether tracking and ero sion is allowed in the Ip tracking and erosion test. Highly filling ATH (>4 0%wt) reduces the number of low unit silicone oligomer precursors which pro mote dry-band arcing as well as the presence of residual carbon which leads to carbonization. Chemical modifications of water vapor liberated from hea ted ATH to methyl groups, which occurs at the thermal decomposition tempera ture of silicone rubber, were found to result in the above process. The pro tection mechanisms of ATH for the tracking and erosion of HTV-SIR are formu lated herein.